Alternating-current generator



(No Model.) 2 Sheets-Sheet 1.

T. A. EDISON. ALTERNATING CURRENT GENERATOR.

No. 470,928. Patented Mar. 15, 1892.

w dmeooao MO F $0M 3313M (No Model.) 2 Sheets-Sheet 2.

T. A. EDISON. ALTERNATING CURRENT GENERATOR.

No. 470,928. Pad tented Mar. 15, 1892.

UNITED STATES PATENT OEEIcE.

THOMAS A. EDISON, OF LLEYVELLYN PARK, NEXV JERSEY.

ALTERNATlNG-CURRENT GENERATOR.

SPECIFICATION forming part of Letters Patent No. 470,928, dated March15,1892.

Application filed August 25, 1891. Serial No. 403,668. (No model.)

To all whom it may concern:

Be it known that I, THOMAS A. EDISON, a citizen of the United States,residing at Llewellyn Park, in the county of Essex and State of NewJersey, have invented a certain new and useful Improvement inAlternating-(Jurrent Generators, (Case No. 926), of which the followingis a specification.

The present invention relates to dynamomachines, and especially to suchmachines for generating alternating currents.

The main objects of the invention are to provide a simple and efficientconstruction of generators of this character by improving theconstruction of the field-magnet and of the frame of the machine and bycertain features of construction, all of which will be hereinafterdescribed.

In the accompanying drawings, Figure 1 is a side view of the generator.Fig. 2 is a detail view illustrating the construction of thefield-magnet. Fig. 3 is a view at right angles to Fig. 1, looking fromthe left; and Fig. 4 shows the fan for cooling the armature.

The base 1 of the machine consists of a heavy casting having at eachside standards 2, to which the journaled bearings 23 are bolted.

The field magnet 4 is circular and is built up in the following manner:A large number of magnetic plates 5, of substantially the form shown inFig. 2, are arranged in parallel circles, the ends of the plates in onecircle overlapping the ends of the plates in adjacent circles. Theplates in any one circle do not meet end to end, but are separated by aconsiderable space, as indicated at 6 in Fig. 1. This makes the body ofthe field-magnet open, so that there is free circulation of air. Theplates 5 are all of the same shape and may be formed by a single stampor die. The plates have a main body, curved to conform to the generalcontour of the field-magnet, and projecting legs 7. These legs are shownat the ends of the plates. When, therefore, the plates are placedtogether in the position already described, the legs of the plates inthe different circles rest directly against each other, so as to formlaminated pole-pieces, the laminations of which are in direct surfacecontact. The plates are provided at the ends with bolt-holes 8, throughwhich the bolts 9 are inserted for binding the plates together.

These bolts also pass through the end cast ings 10. The castings consistof ring-shaped bodies with supporting-legs 11, which are bolted to thebase. On the pole-pieces which are integral with the body of thefield-magnet, since they are formed by projecting legs 7, as described,the field-magnet coils 12 are wound so as to produce alternate andpoles. Centrally within the field-magnet is mounted any suitablearmature 13 on a shaft 14. The core of the armature is preferablycomposed of oxidized iron wire or of sheet-metal rings or plates. It isdeemed unnecessary to describe in detail the construction and winding ofthe armature. The brushes are carried at the ends of the arm 15 by therods 16 and bear on continuous rings, to which the terminals of thearmature-wire are connected in a manner well understood.

In the thin annular space between the armature and magnet poles I placea strip of sheet-iron 1, preferably joining the ends of the strip so asto form a closed ring or cylinder. This sheet-iron strip, plate, orringis in direct contact with the poles of the magnet, and is held inplace by the magnetism thereof without special fastening devices. Whenthe armature rotates, this ring remains stationary, being mechanicallyindependent of the armature. It is found that the use of this sheet-ironring adds very materially to the efficiency of the generator. It alsoreduces the heating effect in the machine, due to Foucault currents.This reduction in the heating effect is probably due to the fact thatthe sheet-iron ring extends or spreads the fields to a certain extent oneach side of the main bodies of the poles in such manner that thechanges of polarity or alternation of current are more gradual than inmachines where the poles are strong and confined to the centers of thefield-magnet coils. Although the sheetiron ring just described reducesthe heat, it is still desirable to provide means for cooling themachine. For this purpose I provide a fan on the shaft 14:. This fanconsists of arms 17 carrying blades 18 so inclined that when theyrevolve with the shaft they will cause a circulation of air around thearmature and magnet poles, and thus cools the same.

What I claim is 1. In an electro magnetic machine, the field- ICO magnethaving several poles and consisting of overlapping magnetic platesbolted together so that the plates shall be in contact at the ends, butshall be separated throughout a portion of their length, said plateshaving main bodies and projecting legs, the latter constituting thefield-magnet poles, sub

stantially as described.

2. In an electro-magnetic machine, the field- V magnet having severalpoles and consisting of overlapping magnetic plates bolted together sothat the plates shall be in contact at the ends, but shall be separatedthroughout magnet, and being in contact with each other,

for a portion only of their lengths, as set forth.

4. The combination, in an electromagnetic machine, of a suitable base,two castings in the form of rings with supporting-legs mounted thereon,a field-magnet consisting of overlapping magnetic plates with projectingpolepieces, and bolts passing through the castings and through theoverlapping ends of the plates, substantially as described.

5. The combination, with a field-magnet and an armature, of a sheet-ironplate resting against or adjacent to all the poles of the magnet, saidplate being mechanically independent of the armature, substantially asdescribed.

6. The combination, with a field-magnet 40 and an armature, of asheet-iron ring or cylinder directly between all of the field-magnetpoles and the armature, and mechanically independent of the latter,substantially as described.

7. The combination, in an electro-magnetic machine, of a laminated openfield-magnet With projecting poles, an armature revolving in front ofsaid poles, and a fan for causing circulation of air, substantially asdescribed.

8. The combination, in an electro-magnetic machine, of a field-magnet, asheet-iron ring resting against the poles of said magnet, an armaturewithin said ring, and a fan for causing circulation of air around thearmature and field-magnet, substantially as described.

This specification signed and witnessed this 31st day of July, 1891.

THOS. A. EDISON.

Witnesses:

JOHN F. RANDOLPH. FREDERICK OTT.

